modifying examples
add function to get Brioulien zone
changing soft confinment potential so it can be imaginary
fixing dimensionality bug in vec_pot. Finishing implementation of 3 vec_pots: SqSin, Gaus, FlatTop, adding fourier transform of pot
fixing problem with plotting complex array
adding kwrds to plot function
comenting out <import envtb.utility.fourier> as the code stops with importing error (works if one do fourier transform). Should be fixed